The purpose of this research is to condition a parameter of cardiac function--ventricular contractility--in normal subjects using operant reinforcement techniques. Contractility relates to the strength of the ventricular beat. It is generally assessed by the rate of change of some cardiovascular variable. Here the maximal slope of the carotid arterial pulse wave recorded externally from the neck (maximal dp/dt) will be used. Simonyi and coworkers (8) have shown the validity of this measure. The operant conditioning procedure involves giving the subject feedback related to his performance. Feedback here will relate to maximal dp/dt. Using a carotid pulse pressure transducer, a differential circuit, and a special purpose digital computer, light flashes will be programmed to occur each time the subject produces a criterion maximal dp/dt--e.g. above a given level, in training to increase it. The subject watches the light display; he is told that a physiological variable controls the light, and that he should try to make the light flash. He is paid for each flash. He is then trained over several days to control maximal dp/dt. Subjects will be taught both to increase and decrease maximal dp/dt. Studies of physiologic mechanisms wll be carried out. These will involve correlations with heart rate and blood pressure data, and studies with drugs which block and stimulate different divisions of the autonomic nervous system. The significance of these studies lies in the further clarification of cardiovascular psychophysiology in normal subjects by the operant conditioning of ventricular contractility. Subsequent studies with patients having conditions which may involve abnormalities of cardiac contractility also are planned.